The present invention relates to an editing system and a video signal output system. More particularly, the invention relates to an editing system and a video signal output system comprising a server using disk drives.
Broadcasting stations and like institutions employ special effect processors that temporarily mix two or more kinds of video signals for video output involving special effects.
Illustratively, the special effect processor provides such special visual effects as fade-in/fade-out, mix, dissolve, wipe and page turn. For fade-in/fade-out, a first video signal is replaced progressively by a second video signal for video output, the first video signal being faded out even as the second video signal is faded in. Mix and dissolve basically involve mixing the first and the second video signals over a certain period of time for output at the point in time of switchover between the two signals. Page turn is one of the nonlinear effects brought about upon switchover between the two video signals.
As shown in FIG. 1, a special effect processor 100 of the above kind has two input terminals 101 and 102. The input terminal 101 receives a signal X which is a first video signal; the input terminal 102 admits a signal Y, a second video signal. The special effect processor 100 adds various special effects to the input signals and outputs a processed video signal from an output terminal 103.
Where the special effect processor 100 is to add such special effects as fade-in/fade-out, mix, dissolve, wipe and page turn to its input signal, it is necessary that the first and the second video signals upon switchover therebetween be input simultaneously to the special effect processor 100 for a predetermined period of time.
That in turn requires that two of the video signals output by external storage devices such as VTR's and disk recording and reproducing devices be input parallelly to the special effect processor 100 at least near the point in time of video signal switchover. Conventionally, at least two signal lines are derived from external storage devices so as to supply necessary video signals to the special effect processor.
The applicant of the present invention already proposed a video signal server (abbreviated to the server hereunder) using a disk storage medium. As depicted in FIG. 2, the server has one or a plurality of input terminals 111 receiving video signals. The input video signals are stored on a disk inside the server 110. The video signals for the scenes requested by users are read from the disk, converted to a necessary transmission format, and sent to the respective users over transmission lines 112.
The server 110 may include a plurality of disks to increase storage capacity and to enhance write speed. Using high-speed read-out techniques, the server 110 offers more output channels than the number of recording and reproducing devices that may be configured.
The server 110 is required to provide a plurality of users simultaneously with the video signals meeting their respective needs. The greater the number of users that the server 110 is capable of simultaneously supplying video signals to, the more valuable the server 110 is considered.
When a user is to edit video signals using the special effect processor 100 of FIG. 1, the user needs to be assigned two channels, i.e., two output ports for the reasons mentioned above. That means a decrease in the number of users who may be supplied simultaneously with their necessary video signals.
Thus when the server 110 is used as part of the special effect processor 100 in the broadcasting station, all users (including an editor and a producer) must be assigned two ports each. This effectively halves the number of users who may be fed simultaneously with the video signals they require. The result is a failure to utilize efficiently the output ports of the server 110.
If the number of users receiving video signals simultaneously is not to be reduced, it is necessary to double the number of available output ports. The requirement entails a need to enlarge the server as a whole; it also means higher costs of the server.